in smooth water(s)

1. Literally, in or on a body of water that is completely still or undisturbed. If you're only comfortable swimming in smooth water, you won't be prepared for the conditions a lifeguard has to face. Kayaking in smooth waters can really quiet the soul. It's not like we can surf in smooth waters, so do you wanna just hang out on the beach?

2. By extension, facing no or very few difficulties or disruptions. We'll be in smooth waters if we can secure a new loan extension from the bank. Investors must not become complacent that the economy is in smooth water, as there are still a number of factors that could lead to another recession. No marriage exists entirely in smooth waters, but as long as you two are prepared to work through life's problems together, you'll be OK.

in smooth water

in quiet and serene circumstances, especially after difficulties.